Mine Detonating Apparatus

ABSTRACT

A steerable mine detonation apparatus is adapted to be pushed by a steered vehicle. The apparatus comprises a frame and at least two spaced apart ground engaging members adapted to support the apparatus and adapted to exert a force on mines in the apparatus&#39; path of sufficient to cause detonation thereof. At least one ground engaging member is steerable, and at least one steerable ground engaging member is attached to the frame so as to pivot with respect thereto about a substantially vertical axis and is connected to a steering linkage, the apparatus further comprising a steering mechanism operatively connected to the steering linkage and, in use, to the pushing vehicle. An actuator adapted to vary the configuration of the steering mechanism, is controlled to provide that, in use, the turning radius of at least a part of the innermost ground engaging member is less than or equal to the turning radius of the innermost wheel of the pushing vehicle, and the turning radius of at least a part of the outermost ground engaging member is greater than or equal to the turning radius of the outermost wheel of the pushing vehicle.

FIELD OF THE INVENTION

The present invention relates to mine detonating apparatus. Theinvention relates particularly, but not exclusively, to mine detonatingapparatus for use with vehicles that are fitted with wheels that aresteered.

BACKGROUND OF THE INVENTION

In regions of conflict it is often necessary for wheeled vehicles to useroads, tracks and other terrain that may have been mined or laid withother improvised explosive devices (IEDs).

Mines and IEDs can be fitted with a variety of different types of fuseshowever they are often fitted with fuses that are designed to detonateas a result of the wheel of the vehicle passing over them, such IEDspossibly including both pressure and time delay fuses. In the remainderof this document the terms mine and IED are used interchangeably andcollectively, i.e. an IED may be a mine and a mine may be an IED.

By detonating as a result of the wheel passing over them, mines explodeso as to inflict the maximum damage to the vehicle, wheel and theassociated steering mechanism.

Relatively small amounts of explosive can easily disable a vehicle.

A mine clearing apparatus intended for use with armoured personnelcarriers (APCs) is described in U.S. Pat. No. 6,915,728. In thisinvention a pair of rollers is pushed in front of the APC in front ofthe tracks and a further set of rollers is towed behind the APC.

The position of the rollers in front of the vehicle is adjusted topartially follow the path of the vehicle by a signal resulting from theposition of a further roller set mounted behind the vehicle.

The invention disclosed here is for a mine roller system that can beattached to a host vehicle or is part of the host vehicle and is pushedahead of the host vehicle so that the path of the wheels of the hostvehicle follow within the path followed by the mine roller system as itgoes round a corner as well as in a straight line.

Mine roller systems that have been designed for use with wheeledvehicles are generally characterised as follows:

They comprise a frame attached to the front of the host vehicle. Theframe is fitted with a number of IED detonating wheels designed to applya downwards force on the ground in front of the vehicle to simulate theeffect of a vehicle passing over them thus activating pressureinfluenced and other fuses that may be used with the IEDs before thevehicle passes over them.

The IED detonating wheels are usually spring loaded to allow them tolift up over local obstacles and down into local hollows and still applya force on the ground. The wheels are grouped into banks that arepivotably mounted onto a frame in such a way as to allow them to casterrelative to the frame. They sometimes have a steering mechanism thatmoves the position of the supporting frame off which the wheels arecastered.

It is apparent that known equipments do not sweep the path of thevehicle very well as the host vehicle goes around a bend in the road.

It is therefore an aim of the invention to overcome or at leastalleviate the problem identified above.

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided an apparatusas specified in Claim 1.

The apparatus may comprise at least two spaced apart steerable groundengaging members, and preferably two spaced apart steerable groundengaging members. Two spaced apart steerable ground engaging members maybe set up to tow in, which assists in the apparatus following a path.

The actuator may be a fluid operated ram, a fluid operated motor, anelectrically operated ram, or an electrically operated motor. A fluidoperated ram could be actuated hydraulically or pneumatically. In thecase where a motor is used rather than a ram, power transmissionapparatus may be provided.

Preferably, the steering mechanism includes a feedback system adapted tomeasure deviation of the apparatus from the path, generate a feedbacksignal and to adjust the steering linkage according to the feedbacksignal to return the apparatus to said path. This provides the advantagethat during use, when the apparatus is subject for forces that causemovement thereof to one side, the steering mechanism adjusts thesteering linkage and hence the steering angle of the steerable groundengaging members to bring the apparatus back to the desired path, forexample after a collision with a stone, or whilst traversing a slope.The apparatus therefore would not run off path for more than a briefperiod.

The feedback signal may be generated mechanically, electronically,electrically or hydraulically.

The steering mechanism may further comprise at least one member arrangedto pivot about a substantially vertical axis.

Advantageously, the steering mechanism comprises first and secondmembers each arranged to rotate about substantially vertical axes,wherein the actuator is adapted to adjust the relative position of thefirst member with respect to the second.

The first and second members may be mounted to rotate about the samesubstantially vertical axis independently of each other.

Preferably, one of the first and second members is operatively connectedto the steering linkage, and the other of the first and second membersmay be operatively connected to the pushing vehicle.

In one embodiment, the steering mechanism comprises a linkage, thelinkage including a tie member pivotably attached at one of its ends toone of the first and second members and operatively attached to thesteering system at its other end. The linkage may further include a tiemember pivotably attached at one of its ends to the other of the firstand second members at its other end to a pushing vehicle.

Preferably, the steering linkage includes a connector mounted on theframe and operatively connected to the or each steerable ground engagingmember, and the steering mechanism. Operative connection of theconnector to the steerable ground engaging members may be achieved bythe use of track rods, and/or the fluid actuators. Operative connectionof the connector to the steering mechanism is advantageously by means ofa tie rod.

At least one ground engaging member may be adapted to follow the path ofthe apparatus set by the at least one steerable ground engaging member.

The apparatus may further including a steering lock providing locked andunlocked configurations of the or each steerable ground engagingmembers. The steering lock may include at least one element movablebetween a locked configuration in which said element engages with a partof the steerable ground engaging member and an unlocked configuration inwhich the said element is disengaged from the steerable ground engagingmember.

Preferably, the actuator is provided with a neutral setting in which theactuator configuration changes according to passive forces exertedthereon. This allows the apparatus to be moved when the steerable groundengaging members are locked. For example, where the actuator ishydraulic, the hydraulic circuit powering the actuator is provided withvalves that permit a float setting to be selected, in which the actuatoris free to extend or retract.

Preferably, the ground engaging members are mounted to pivot about asubstantially horizontal axis.

Each steerable ground engaging member may include a plurality ofindividual ground engaging elements, each element preferably beingmounted to move independently in a substantially vertical plane.

Another aspect of the invention provides the combination of a pushingvehicle and connect thereto a steerable mine detonation apparatusadapted to be pushed by a steered vehicle, the apparatus comprising aframe, at least two spaced apart ground engaging members adapted tosupport the apparatus and adapted to exert a force on mines in the paththereof sufficient to cause detonation thereof, wherein at least oneground engaging member is steerable, and wherein the at least onesteerable ground engaging member is attached to the frame so as to pivotwith respect thereto about a substantially vertical axis and isconnected to a steering linkage, the apparatus further comprising asteering mechanism operatively connected to the steering linkage andincluding an actuator adapted to vary the configuration of the steeringmechanism, and a control means including a controller configured toreceive an input signal related to the turning radius of a pushingvehicle and to generate an actuator control signal related to the inputsignal, and to control the actuator according to the actuator controlsignal, wherein the so controlled actuator configures the steeringmechanism to adjust the steering linkage such that the at least onesteerable ground engaging member is positioned to follow a path whichprovides that, in use, the turning radius of at least a part of theinnermost ground engaging member is less than or equal to the a turningradius of the innermost wheel of the pushing vehicle, and the turningradius of at least a part of the outermost ground engaging member isgreater than or equal to the a turning radius of the outermost wheel ofthe pushing vehicle.

As mentioned above, in clearing mines and IEDs, it is particularlyimportant that the mine rollers should cover the path that the wheels ofthe pushing vehicle will traverse. The invention accomplishes this.Further, the invention provides an apparatus configured such that itreturns to the required path automatically after being subjected to aforce causing deviation of the apparatus from the path. Still further,the apparatus of the invention provides for the mine rollers to bespaced from the pushing vehicle by a significantly greater distance thanis the case mine rollers of the prior art. This means that in the eventof a mine being detonated, the risk of the pushing vehicle being damagedis much reduced, the maximum pressure of the explosion diminishes withthe cube of the distance from source of the explosion, and henceincreasing the distance between the rollers and the pushing vehicle hasa marked effect on the likelihood of the vehicle being damaged by anexplosion.

BRIEF DESCRIPTION OF THE DRAWINGS

The Drawings illustrate preferred embodiments of the invention, and areby way of example only.

FIG. 1 is a plan view of a known mine clearance roller.

FIG. 2 is a plan view of a device according to a first embodiment of theinvention on a straight heading.

FIG. 3 is a side view of the device illustrated in FIG. 2.

FIG. 4 is a plan view of the device illustrated in FIGS. 2 and 3unhitched from the pushing vehicle.

FIG. 5 is a side view of the device illustrated in FIG. 4.

FIG. 6 is a plan view of the device illustrated in FIGS. 4 and 5 lockedfor reversing.

FIGS. 7 to 12 illustrate the combination of the device and the pushingvehicle executing a turn where:

FIG. 7 is a plan view of the device travelling on a straight path justprior to commencing a turn to the left;

FIG. 8 is a plan view of the device illustrated in FIG. 7 with thesteering wheels of the pushing vehicle turned to the left to an angle ofapproximately 10 degrees to commence the turn;

FIG. 9 is a plan view of the device established on a turn with thepushing vehicle's steering wheels set at a steering angle ofapproximately 10 degrees;

FIG. 10 is a plan view of the device moving on to a smaller turningradius with the steering wheels of the pushing vehicle turned to theleft to an angle of approximately 20 degrees;

FIG. 11 is a plan view of the device established on a turn with thepushing vehicle's steering wheels set at a steering angle ofapproximately 20 degrees; and

FIG. 12 is a plan view of the device established on a turn with thepushing vehicle's steering wheels set at a steering angle ofapproximately 40 degrees.

FIG. 13 is a schematic representation of parts of the alignment linkageof the first embodiment of the invention.

FIG. 14 is a side view of a ground engaging wheel of the device.

FIG. 15 is a front view of the device.

FIG. 16 is a plan view of a device according to another embodiment ofthe invention on a straight heading

FIG. 17 is a plan view of the device illustrated in FIG. 17 executing aturn.

FIG. 18 is a plan view of the device following a deviation thereof froma desired path.

DETAILED DESCRIPTION OF THE PRIOR ART EMBODIMENT

The sketch in FIG. 1 shows one possible arrangement of a known system.The sketch shows the plan view of a vehicle fitted with three rollersets at its front travelling around a bend from right to left.

In FIG. 1, about one third of the path followed by the vehicle would notbe swept by the rollers. This is a concern because seeing theoperational capabilities of existing equipment, the enemy can simplyplant their IEDs on the bends in the road and easily defeat an existingroller system.

If the framework is steered using a mechanism that reacts these forcesagainst the host vehicle, the forces required to steer tend to induceloads much higher than intended on the front wheels and steeringmechanism of the host vehicle. This is likely to result in increasedwear and premature failure of the steering mechanism of the hostvehicle.

It is also apparent that the spring loaded wheels that are intended todetonate mines and other IEDs are sometimes very close to the body ofthe host vehicle.

It is well known that the effectiveness of an explosive blast reduceswith increased distance. With the detonating wheels so close to thevehicle the detonation created by them usually causes substantial damageto the vehicle and puts the crew of the vehicle at increased risk.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention serves to overcome some of the limitations ofexisting inventions.

The mine roller system disclosed here is pushed ahead of the hostvehicle in such a way that the path of the wheels of the host vehicleautomatically follows more closely within the path covered by the mineroller system as it goes round a corner as well as in a straight line.It is possible, particularly in a tight turn, that during the periodbetween the steering wheels of the pushing vehicle being turned and themine roller system reacting, the path taken by the wheels of the pushingvehicle may not be covered completely. This may be overcome by theprovision of a manual override system to steer the mine roller system inadvance of the steering wheels of the pushing vehicle for example.

The mechanism invented induces small additional loads on the steeringmechanism of the host vehicle thus reducing the likelihood of excessivewear and premature failure of the host vehicle systems.

The mine rollers are pushed ahead of the host vehicle a substantialdistance away from the front of the vehicle thereby reducing the risk ofinjury to the crew of the host vehicle and damage to the vehicle.

In the following description we describe the use of the equipment with afour wheel drive truck (however, the fact that the truck has four wheeldrive is not relevant).

We envisage that it will be practical to adjust the weight of the mineroller system if required depending on the vehicles with which thesystem is being used.

The steering mechanisms invented are shown diagrammatically in FIGS. 2to 18:

Notice the substantial “stand off” distance achieved between the wheelsets of the mine roller system and the front of the pushing vehicle.

Referring particularly to FIGS. 16 and 17, in these drawings the wheeledhost vehicle, is shown in plan view, with the mine roller system (MRS)fitted in front of it. The arrangement comprises the frame (4) connectedto the vehicle (10) along the centre line. The frame can conveniently bemounted onto the NATO pintle usually found on the front of militaryvehicles. Mine roller sets (1), (2), and (3) are pivotally attached tothe frame (4), so that they can caster about substantially verticalaxes. Roller set (3) is further pivotally attached to the frame (4) byan intermediate bracket (11).

In operation, the linkage system, schematically indicated by elements(5), (6), (7) and (8) serves to automatically steer the roller sets (1)and (2) to keep them on a path in front of the vehicle. If the rollerbecomes out of line or the host vehicle makes minor steeringadjustments, the linkage geometry is such that it will serve to maintainthe roller sets (1) and (2) in front of the vehicle. Roller set (3) isfree to caster 360 degrees. The roller set is not steered, it simplyfollows the path taken by the roller sets (1) and (2).

FIG. 17 shows a plan view of the mine roller system pushed by thevehicle, travelling around a bend.

Note how the front roller sets are steered closely along the path thatthe wheels of the host vehicle follow.

This is made possible by the geometry chosen for the linkage. The anglethat the frame of the mine roller system needs to take is indicated as“A” in FIG. 17. Notice how the roller sets are in line with the frame.This is made possible by adjusting the length of linkage member (5).

The required length for linkage member (5) is determined by measuringthe turning circle being negotiated. This is done electronically by useof a simple linear transducer or some other measuring device connectedto the vehicle's steering mechanism. The measuring device may measureany parameter of the vehicle's steering mechanism from which thevehicle's turning circle may be calculated. From this electronicmeasurement, the programmable logic controller (PLC) programmecalculates the required angle “A” according to an algorithm (which isnot disclosed herein, the algorithm being within the knowledge of theperson skilled in the art) and the required length of linkage member(5).

When negotiating a bend of a particular turning circle, the mine rollersare automatically steered on the required path. In the same way as whenthe required steering angle “A” is zero ie when travelling in a straightline, small deviations in steering angle of the host vehicle arecompensated for by automatic tracking of the steering mechanism. If themine rollers become out of line, the linkage automatically adjusts tocompensate and steer the roller set into line.

In practice the linkage member (5) is a hydraulic cylinder. Theextension i.e. the position of this is accurately controlled by use ofan integral linear transducer and electronic closed loop feedbacksystem.

The hydraulic cylinder (5) is only actuated when the turning circlechanges. At constant turning circles and in a straight line the cylinderdoesn't extend or retract. The steering is automatically maintained inthe correct position by the mechanism. This is important because itmeans that the minimum amount of power is used and the auxiliaryhydraulic power pack required remains small and can be powered from thehost vehicle inter-vehicle starting socket. It also means that it is notnecessary to constantly correct for small steering misalignments this isachieved automatically with no hydraulic power consumption.

As the wheels of the host vehicle are steered, the turning radius thatwill be created is calculated from measurements received from atransducer fitted to the steering mechanism of the vehicle. The PLC isprogrammed to calculate the angle “A” that the frame is required toadopt to ensure that the host vehicle will follow the roller sets. Thecontrol circuitry then serves to actuate the hydraulic cylinder so as torotate the link 5 a. This causes the wheelsets to steer so as to bringthe framework to the appropriate angle.

Referring now to FIGS. 2 to 6, there is shown another embodiment of theinvention. Where parts of the embodiment now described correspond toparts of the device described with reference to FIGS. 16 and 17, likereference numerals are used.

Referring first to FIGS. 2 to 6, the mine roller apparatus 20 comprisesa frame 4, which includes an A frame formed by structural members 22,23, formed for example from tubular steel. A push bar 21 extends fromthe apex of the A-frame and terminates in a hook 21 a, which attaches toa pintle 9 of the pushing vehicle. Frame 4 supports a shaft 25, which ishollow in the illustrated example, and which extends in a substantiallyperpendicular direction to the longitudinal axis of the apparatus 20.Two elements of the mine roller steering mechanism are mounted on theshaft 25. The first is an elongate member 24 which includes a bracket 26attached to the end of the member 24 proximate the A frame through whichthe shaft 25 passes. A bracket 27 is attached to the elongate member 24towards the free end thereof. One end of a rod 28 is pivotally connectedto the bracket 27, the other end of the rod being pivotally connected tothe pushing vehicle 10 by means of a pivot attachment 29. The rod 28forms part of a feedback system. The elongate member 24 mounts anotherbracket 30 to which one end of an extensible actuator 31, in the form ofa hydraulic ram in the present example, is attached. The other end ofthe actuator 31 is attached to a bracket 26 by a pivot attachment 32,which may comprise a pin passing through holes in the bracket 26 and endof the actuator 31. The bracket 26 is also pivotally mounted on theshaft 25, that is it may rotate about the shaft 25. The actuator 31serves to change the angle of the member 24 relative to the bracket 26.A tie rod 36 extends between and is pivotally attached to the bracket 26at pivot attachment 33 and a plate 35 of a roller steering linkage. Theplate 35 is pivotably attached to a bracket 58, which is attached to theframe 23 by a bracket 59. The shaft 25, elongate member 24 and bracket26 are illustrated in detail in FIG. 13.

The apparatus includes a steering angle sensor for sensing the steeringangle of the steering wheels (the front wheels) of the pushing vehicle10. Of course the steering angle of the steering wheels need not bemeasured directly. Any measuring device connected to the pushingvehicle's steering mechanism, and arranged to measure a parameter of thevehicle's steering mechanism from which the vehicle's turning circle maybe calculated may be used. The PLC runs an algorithm that calculates thelength at which actuator 31 must be set to move the roller sets 1, 2 toa position in which the roller sets pass over the track of the innermost wheel of the pushing vehicle (this corresponds approximately to thecalculation of the length of the actuator 5 to provide angle A describedwith reference to FIGS. 2 and 3).

In this example the rod 28 is of fixed length. Hence, the rod 28, thepush bar 21 the elongate member 24 and the part of the front of thepushing vehicle 10 extending between the pintle 9 and the pivotattachment 29 form a parallelogram linkage.

The movement of the mine clearance apparatus will now be described withreference to FIGS. 7 to 9 and 10 to 12. In FIG. 7 the pushing vehicle 10is just about to commence a turn to the left. In FIG. 8 the pushingvehicle 10 has turned the front wheels 10 a, 10 a ¹ to the left. As thewheels of vehicle are being steered to the left, the steering anglesensor detects the angle through which the front wheels have been turned(10 degrees in this case) and the PLC calculates the require length ofactuator 31 to position the mine clearance apparatus 20 in relation tothe pushing vehicle 10 such that the path followed by at least a part ofthe roller set 2 (the inner roller set when turning to the left) passesover the path that the unsteered inner wheel of the pushing vehicle (inthe example the left hand rear wheel) will follow when executing theturn.

Hence, when the actuator 31 is retracted to the length required by PLC,the plate 35 is caused to rotate anti-clockwise. The roller sets 1, 2are connected to the plate 35 by track rods 7, 8, and hence turning theplate 35 anti-clockwise in turn turns the roller sets 1, 2anti-clockwise.

With the roller sets 1, 2 set in the position illustrated in FIG. 8 themine clearance apparatus 20 tracks across to the left towards thedesired position as the apparatus is pushed forwards. As the apparatus20 moves from the position illustrated in FIG. 8 to the position shownin FIG. 9, the change in shape of the above-mentioned parallelogramcauses the plate 26 and hence the plate 35 to turn clockwise until theposition illustrated in FIG. 8 is reached where the assumed steeringangle of roller sets 1, 2 corresponds to that which is required to keepthe apparatus 20 on the turning radius that ensures that the pathtraversed by at least a part of the inner roller set 2 covers the pathtraversed by the left rear wheel 10 b of the vehicle 10, and the pathtraversed by at least a part of the outer roller set 1 covers the pathtraversed by the right front wheel 10 a′ of the pushing vehicle 10.

In FIG. 10 the driver of the pushing vehicle has turned to wheels 10 a,10 a ¹ to increase the turning angle to 20 degrees, this increase insteering angle occurring as the vehicle moves forwards. Again, the PLCdetermines the required length of actuator 31 and causes the lengththereof to be changed. The roller sets 1, 2 are turned anti-clockwiseand the apparatus tracks across to the left to assume to positionillustrated in FIG. 11, in which the path traversed by the wheels of thepushing vehicle are covered by the rollers 1, 2.

In FIG. 12, the driver of the pushing vehicle 10 has increased thesteering angle to 40 degrees, the change in steering angle resulting inthe length of the actuator decreasing to provide the required angle A.The apparatus tracks across to the left.

In each of the Figures referred to above, a roller set 3 is illustrated.The roller set 3 is situated between roller sets 1 and 2, and is notsteering in the same manner as roller sets 1 and 2. Roller set 3 isattached to the structural member 23 by means of a pivot linkage 60comprising a towing eye 62 extending from a draw bar of the roller set3, a clevis hitch 64 and a pin 6 configured to pass through alignedholes in the towing eye 62 and clevis hitch 64 (see FIG. 5 inparticular).

In the Figures the outer roller sets 1, 2 are steerable and the centreroller set 3 is unsteered, but follows the steered path because it isconnected to the apparatus as described above. It may be envisaged thatthe centre roller set may be steered as well as the outer roller sets.Further, it may be envisaged that the centre roller may be steered andthe outer rollers unsteered, but connected to the apparatus in a mannerthat provides for them to be able to follow the path determined by thesteered centre wheel set, for example using the method of attachment tothe structural member 23 as described above in relation to roller set 3.

In addition to providing for the roller sets 1, 2 to clear the path ofthe inner most wheel of the pushing vehicle, the linkage arrangement ofthe apparatus and its geometry provide that the apparatus will alwayscome to an equilibrium position corresponding to the steering angle andhence desired path of the pushing vehicle and will return to the desiredpath after any deviation therefrom, i.e. the linkage arrangementprovides a feedback system. This feature is now described with referenceto FIGS. 2 and 18. Referring to FIG. 2, if for example, one of therollers were to hit a large stone and the apparatus 20 were thrownacross to the right to the position illustrated in FIG. 18, without thedriver of the pushing vehicle 10 making any corrective steering input,the apparatus 20 would be caused to return to the set steered pathbecause the deviation of the apparatus to the right would cause theshape of the parallelogram to change causing the elongate member 24 torotate anti-clockwise about shaft 25, which due to the fixed length ofactuator 31 causes the bracket 26 to rotate anti-clockwise about shaft25, which due to the action of the tie rod 36 causes the plate 35 toalso rotate anti-clockwise, which in turn causes the roller sets 1 and 2to take up a position to steer the apparatus 20 to the left. As theapparatus 20 returns to the desired path the parallelogram returns tothe correct shape for the desired path and the combination of theapparatus and pushing vehicle return to a steady state. In this examplethe feedback signal representing the deviation of the apparatus from thedesired angle A, is provided by the mechanical linkage, in particular,the mechanical link attaching the steering mechanism to the vehicleprovided by rod 28. However, the feed back system need not be whollymechanical arrangement. For example, the link 28 could be replace with alinear actuator, one end being connected to the elongate member 24 andthe other to a fixed part of the apparatus, for example the push bar 21.A transducer may be provided to generate an electronic signalrepresentative of the actual angle A, which may be compared with thecalculated angle A. The controller may be programmed to generate asignal which is used to adjust the length the actuator and henceincrease the steering angle of the roller sets 1, 2 to bring theapparatus back such that the angle A is the calculated angle A. Such anelectronic feed back arrangement would operate on a continuous loop andadjust the length of the actuator as the apparatus returned to thedesired path, or upon the return of the apparatus to the calculatedangle A. Electronic communication between the pushing vehicle 10 and theapparatus may be by wire or wireless.

An alternative electronic feedback signal could utilise the actuator 31.In such an arrangement, the link 28 would be removed, and the actuatorwould extend between a fixed object and the bracket 26, for example theposition of member 24 may fixed. The required length of actuator 31 toprovide the required angle “A” would be calculated as described above.If the apparatus were to hit an object resulting in a deviation to theright, the actual angle A would not correspond to the required angle A.This difference may be used to calculate a new length of actuator 31 toadjust the steering angle of the roller sets 1, 2 to bring the apparatusback to the path as described in the preceding paragraph.

A feature of the apparatus 20 is that whilst it is inherently stablewhilst being pushed forward, it is inherently unstable when the pushingvehicle is reversed. It would be undesirable for reversing thecombination of the pushing vehicle 10 and apparatus 20 to be difficult.To alleviate the problem of inherent instability when reversing, theapparatus 20 includes reversing locks 40, which in the illustratedexample are operable remotely from the cab of the pushing vehicle 10.Referring specifically to FIGS. 4 and 6, each reversing lock 40comprises a swing arm 41, one end of which is pivotally connected to abracket 42 mounted on the structural member 23. An actuator 44, in theform of a hydraulic ram in the illustrated example, is pivotallyattached to the other end of the swing arm 41, and to bracket 45 whichis mounted on the structural member 23. The reversing lock also includesa stop 46.

In FIG. 6, both roller sets 1, 2 are locked. In the locked state, it canbe seen that the actuator 44 is extended and the swing arm 41 is inengagement with the stop 46 which is attached to the roller mount, andsimilarly, swing arm 41 a is in engagement with its corresponding stop.Hence, rotation of the roller sets 1, 2 about their substantiallyvertical axes is prevented.

In FIG. 4, the steering locks 40 associated with the roller sets 1 and 2are shown in its unlocked state. In this state the roller set 2 mayrotate about its substantially vertical axis, the range of rotation tothe left being limited by the engagement of the stop 46 with the surface41′ of the swing arm 41. Roller set 1 may rotate about its substantiallyvertical axis in a counter clockwise direction to an amount limited bythe engagement stop 46 with the surface 41′ of the swing arm 41.

With the steering lock in the locked configuration, pivotal movementbetween the pushing vehicle 10 and the apparatus 20 must be provided forin order for the combination to execute a turn. This could be achievedin a number of ways. For example, the rod 28 may be detached, or the tierod 36 may be detached. However, both of these methods would require aperson to walk from the pushing vehicle 10 to the apparatus 20. Giventhat there is potential for unexploded IED's to be present, it is highlydesirable that the operator should remain in the vehicle. Hence, thepreferred means of providing for pivotal movement between the pushingvehicle 10 and the apparatus 20 is to provide the valve controlling thelength of actuator 31 with a float setting, and a control means in thecab of the vehicle 10 to allow the valve to be switched to float mode.With the actuator in float mode the elongate member 24 is free to pivotabout shaft 25 and hence the vehicle 10 may pivot with respect to theapparatus 20.

The roller set 3 is simply lifted clear of the ground during reversing,for example by means of a winch or hydraulic ram.

Referring now to FIG. 14, each roller 56 of the roller sets 1 to 3 ismounted to pivot about a substantially horizontal axis, and a biasingmeans 57 (such as a gas spring, coil spring or hydraulic ram andaccumulator) is provided to ensure that each individual roller 56follows the surface over which it traverses.

Referring now to FIGS. 14 and 15, each roller set 1, 2 is mounted onpivot mount 50, the pivot axis of which lies in a substantiallyhorizontal plane about a pin 52. Further, the wheel is 56 is mounted ona bracket 55 which is in turn pivotaly mounted on a bracket 54 by meansof a pin or the like, the bracket 54 being connected to a plate which ismounted on the pin 52. A biasing means, such as a gas spring (or coilspring, or a hydraulic ram and accumulator or any other suitable biasingmeans) 57 extends between the bracket 55 and the plate 53. Such amounting provides for the roller sets 1, 2, 3 to follow groundundulations and mitigates against IED's being missed simply because theylie in a hollow between the extreme edges of the roller sets 1 to 3.Regarding the roller set 3, roll movement of the roller set may beaccommodated by a pivot mount extending rearward from the drawbar 61substantially along the axis of the drawbar, or alternatively, thehitching of the drawbar 61 to the frame may include a ball hitch or aball link.

Ballast weights 51 may be provided to ensure that there is adequateweight on the wheels 56 of rollers 1 to 3.

The extension of the ram 31 is preferably not abrupt. Advantageously,the steering angle of the vehicle is sensed at small time intervals sothat the change the length of the ram 31 occurs gradually so that inpractice the cylinder moves and wheelsets start to turn as the vehiclestarts to turn.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A steerable mine detonation apparatus adapted to be pushed by asteered vehicle, the apparatus comprising a frame, at least two spacedapart ground engaging members adapted to support the apparatus andadapted to exert a force on mines in the path thereof sufficient tocause detonation thereof, wherein at least one ground engaging member issteerable, and wherein the at least one steerable ground engaging memberis attached to the frame so as to pivot with respect thereto about asubstantially vertical axis and is connected to a steering linkage, theapparatus further comprising a steering mechanism operatively connectedto the steering linkage and including an actuator adapted to vary theconfiguration of the steering mechanism, and a control means including acontroller configured to receive an input signal related to the turningradius of a pushing vehicle and to generate an actuator control signalrelated to the input signal, and to control the actuator according tothe actuator control signal, wherein the so controlled actuatorconfigures the steering mechanism to adjust the steering linkage suchthat the at least one steerable ground engaging member is positioned tofollow a path which provides that, in use, the turning radius of atleast a part of the innermost ground engaging member is less than orequal to the a turning radius of the innermost ground engaging member ofthe pushing vehicle, and the turning radius of at least a part of theoutermost ground engaging member is greater than or equal to the aturning radius of the outermost ground engaging member of the pushingvehicle.
 2. Apparatus according to claim 1, comprising at least twospaced apart steerable ground engaging members.
 3. Apparatus accordingto claim 1, wherein the actuator is selected from the group comprising afluid operated ram, a fluid operated motor, an electrically operatedram, and an electrically operated motor.
 4. Apparatus according to claim1, wherein the steering mechanism includes a feedback system adapted tomeasure deviation of the apparatus from the path, generate a feedbacksignal and to adjust the steering linkage according to the feedbacksignal to return the apparatus to said path.
 5. Apparatus according toclaim 4, wherein the feedback signal is generated mechanically. 6.Apparatus according to claim 4, wherein the feedback signal is generatedelectronically.
 7. Apparatus according to claim 1, the steeringmechanism further comprising at least one member arranged to pivot abouta substantially vertical axis.
 8. Apparatus according to claim 7,comprising first and second members each arranged to rotate aboutsubstantially vertical axes, wherein the actuator is adapted to adjustthe relative position of the first member with respect to the second. 9.Apparatus according to claim 8, wherein the first and second members aremounted to rotate about the same substantially vertical axisindependently of each other.
 10. Apparatus according to claim 8, whereinone of the first and second members is operatively connected to thesteering linkage.
 11. Apparatus according to claim 10, wherein the otherof the first and second members is operatively connected to the pushingvehicle.
 12. Apparatus according to claim 10, wherein the steeringmechanism comprises a linkage, the linkage including a tie memberpivotably attached at one of its ends to one of the first and secondmembers and operatively attached to the steering system at its otherend.
 13. Apparatus according to claim 10, wherein the linkage furtherincludes a tie member pivotably attached at one of its ends to the otherof the first and second members at its other end to a pushing vehicle.14. Apparatus according to claim 1, wherein the steering linkageincludings a connector rotatably mounted on the frame and operativelyconnected to the or each steerable ground engaging member, and whereinthe steering mechanism is operatively attached to the connector. 15.Apparatus according to claim 1, further comprising at least one groundengaging member adapted to follow the path of the apparatus set by theat least one steerable ground engaging member.
 16. Apparatus accordingto claim 1, further including a steering lock providing locked andunlocked configurations of the or each steerable ground engagingmembers.
 17. Apparatus according to claim 16, wherein the steering lockincludes at least one element movable between a locked configuration inwhich said element engages with a part of the steerable ground engagingmember and an unlocked configuration in which the said element isdisengaged from the steerable ground engaging member.
 18. Apparatusaccording to claim 16, wherein the actuator is provided with a neutralsetting in which the actuator configuration changes according to passiveforces exerted thereon.
 19. Apparatus according to claim 1, whereinground engaging members are mounted to pivot about a substantiallyhorizontal axis.
 20. Apparatus according to claim 1, wherein eachsteerable ground engaging member includes a plurality of individualground engaging elements, each element being mounted to moveindependently in a substantially vertical plane.
 21. The combination ofa pushing vehicle and connect thereto a steerable mine detonationapparatus adapted to be pushed by a steered vehicle, the apparatuscomprising a frame, at least two spaced apart ground engaging membersadapted to support the apparatus and adapted to exert a force on minesin the path thereof sufficient to cause detonation thereof, wherein atleast one ground engaging member is steerable, and wherein the at leastone steerable ground engaging member is attached to the frame so as topivot with respect thereto about a substantially vertical axis and isconnected to a steering linkage, the apparatus further comprising asteering mechanism operatively connected to the steering linkage andincluding an actuator adapted to vary the configuration of the steeringmechanism, and a control means including a controller configured toreceive an input signal related to the turning radius of a pushingvehicle and to generate an actuator control signal related to the inputsignal, and to control the actuator according to the actuator controlsignal, wherein the so controlled actuator configures the steeringmechanism to adjust the steering linkage such that the at least onesteerable ground engaging member is positioned to follow a path whichprovides that, in use, the turning radius of at least a part of theinnermost ground engaging member is less than or equal to the a turningradius of the innermost ground engaging member of the pushing vehicle,and the turning radius of at least a part of the outermost groundengaging member is greater than or equal to the a turning radius of theoutermost ground engaging member of the pushing vehicle.